The present invention relates to rear under-ride protection for motor vehicles. In particular, the present invention relates to a hinged bumper that avoids damage to the bumper in the event of a vertical force to the bumper.
The U.S. Department of Transportation (xe2x80x9cU.S. D.O.T.xe2x80x9d), Federal Highway Administration has prescribed safety regulations for federal motor carriers which in relevant part address rear end protection for motor vehicles. Specifically, motor vehicles manufactured after Dec. 31, 1952 which have a ground clearance at the rear end of more than thirty inches from the ground are required to have a bumper substantially constructed and firmly attached to the vehicle at a height of no more than thirty inches above the ground. In addition, the bumper may not be located more than twenty four inches forward of the extreme rear of the vehicle. The objective of this regulation is to ensure that the bumpers of larger motor vehicles approximate the height of the bumpers of smaller motor vehicles and thereby prevent, in the event of a collision, the smaller vehicles from under-riding the rear end of larger vehicles.
One way large vehicle operators have complied with this safety regulation is by welding or bolting a metal bumper to the frame of the motor vehicle. In such a case, a pair of spaced supports which carry the bumper are attached to the frame. The length and angle of the supports are selected to properly position the bumper. The bumper itself is typically formed from a heavy gauge metal beam and is welded to the supports.
Damage to the bumper other than by rear end vehicle collisions can occasionally occur. For example, for motor vehicles that operate on or off road, such as concrete mixing trucks, may encounter changes in ground elevation as the trucks are backing up, or as they are moving forward, which can result in rear bumper contact. Such contact between prior art bumpers and the ground can result in a vertical force being applied to the bumper. Other conditions may also result in a vertical force being applied to the bumper. If the vertical force from the contact is sufficient, a partial or complete bending of the bumper can result, with a consequent change in its elevation from level ground or its forward position relative to the extreme rear of the vehicle. This in turn requires that the bumper be repaired, if possible, or replaced, before the vehicle is again in compliance with the federally prescribed safety regulations. Thus, while the above described prior art bumpers comply with the safety regulations, their maintenance requires considerable time and expense. There is a need for an improved rear under-ride protection device for a motor vehicle that meets federal safety regulations and minimizes the time and cost of maintaining such a device.
The bumper system of the present invention connects to the spaced frame members of a motor vehicle frame. The bumper system comprises a pair of brackets, each bracket having a first portion that is connectable to one of the frame members, and a second portion which provides a support surface. Connected to each bracket is an arm. A first end of each arm is pivotally connected to the second portion of one of the brackets. When the bracket is mounted to a frame member, the arm is supported by the support surface when the arm is in a first position, but the arm is movable about the pivotal connection. A bumper section having first and second ends is connected to the second end of each arm